What's New in Nanotechnology?

Stanford University engineers have developed a low-cost, plastic-based textile that, if woven into clothing, could cool your body far more efficiently than is possible with the natural or synthetic fabrics in clothes we wear today. The researchers suggest that this new family of fabrics could become the basis for garments that keep people cool in hot climates without air conditioning. “If you can cool the person rather than the building where they work or live, that will save energy,” said Yi Cui, an associate professor of materials science and engineering at Stanford and of photon science at SLAC National Accelerator Laboratory. This new material works by allowing the body to discharge heat in two ways that would make the wearer feel nearly 4 degrees Fahrenheit cooler than if they wore cotton clothing.The material cools by letting perspiration evaporate through the material, something ordinary fabrics already do. But the Stanford material provides a second, revolutionary cooling mechanism: allowing heat that the body emits as infrared radiation to pass through the plastic textile. To develop their cooling textile, the Stanford researchers blended nanotechnology, photonics and chemistry to give polyethylene – the clear, clingy plastic we use as kitchen wrap – a number of characteristics desirable in clothing material: It allows thermal radiation, air and water vapor to pass right through, and it is opaque to visible light.

Graphene, the atomically thin sheets of carbon that materials scientists are hoping to use for everything from nanoelectronics and aircraft de-icers to batteries and bone implants, may also find use as contrast agents for magnetic resonance imaging (MRI), according to new research from Rice University. “They have a lot of advantages compared with conventionally available contrast agents,” Rice University researcher Sruthi Radhakrishnan said of the graphene-based quantum dots she has studied for the past two years. “Virtually all of the widely used contrast agents contain toxic metals, but our material has no metal. It’s just carbon, hydrogen, oxygen and fluorine, and in all of our tests so far it has shown no signs of toxicity.” “There are tried-and-true methods for attaching biomarkers to carbon nanoparticles, so one could easily envision using these quantum dots to develop tissue-specific contrast agents,” Ajayan said. “For example, this method could be used to selectively target specific types of cancer or brain lesions caused by Alzheimer’s disease. That kind of specificity isn’t available with today’s contrast agents.” Radhakrishnan said her work began in 2014 after Ajayan’s research team found that adding fluorine to either graphite or graphene caused the materials to show up well on MRI scans. Radhakrishnan said she plans to continue studying the material and hopes to eventually have a hand in proving that it is safe and effective for clinical MRI tests. “I would like to see it applied commercially in clinical ways because it has a lot of advantages compared with conventionally available agents,” she said.

Researchers at Washington University School of Medicine in St. Louis have shown in mice that they can inject nanoparticles into an injured joint and suppress inflammation immediately following an injury, reducing the destruction of cartilage. In the study, the nanoparticles were injected shortly after an injury, and within 24 hours, the nanoparticles were at work taming inflammation in the joint. But unlike steroid injections that are quickly cleared, the particles remained in cartilage cells in the joints for weeks. The nanoparticles used in the study are more than 10 times smaller than a red blood cell, which helps them penetrate deeply into tissues. The particles carry a peptide derived from a natural protein called melittin that has been modified to enable it to bind to a molecule called small interfering RNA (siRNA). The melittin delivers siRNA to the damaged joint, interfering with inflammation in cells. The peptide-based nanoparticle was designed by study co-investigators Hua Pan, PhD, an assistant professor of medicine, and Samuel Wickline, MD, the James R. Hornsby Family Professor of Biomedical Sciences. The nanoparticles were injected shortly after injury to prevent the cartilage breakdown that eventually leads to osteoarthritis. Whether such a strategy will work years after an injury, when osteoarthritis is established and there is severe cartilage loss, still needs to be studied. But the findings suggest that the nanoparticles, if given soon after joint injuries occur, could help maintain cartilage viability and prevent the progression to osteoarthritis.

A new tool that uses a forest-like array of vertically-aligned carbon nanotubes that can be finely tuned to selectively trap viruses by their size can increase the detection threshold for viruses and speed the process of identifying newly-emerging viruses. The research was led by an interdisciplinary team of scientists at Penn State. "Detecting viruses early in an infection before symptoms appear, or from field samples, is difficult because the concentration of the viruses could be very low -- often below the threshold of current detection methods," said Mauricio Terrones, professor of physics, chemistry, and materials science and engineering at Penn State, and one of the corresponding authors of the research. "Early detection is important because a virus can begin to spread before we have the ability to detect it. The device we have developed allows us to selectively trap and concentrate viruses by their size -- smaller than human cells and bacteria, but larger than most proteins and other macromolecules -- in incredibly dilute samples. It further increases our ability to detect small amounts of a virus by more than a hundred times." The research team developed and tested a small, portable device that increases the sensitivity of virus detection by trapping and concentrating viruses in an array of carbon nanotubes. Dilute samples collected from patients or the environment are passed through a filter to remove large particles such as bacteria and human cells, then through the array of carbon nanotubes in the device. Viruses get trapped and build up to usable concentrations within the forest of nanotubes, while other smaller particles pass through and are eliminated. The concentrated virus captured in the device can then be put through a panel of tests to identify it, including molecular diagnosis by polymerase chain reaction (PCR), immunological methods, virus isolation, and genome sequencing.

Rutgers University engineers have found a simple method for producing high-quality graphene that can be used in next-generation electronic and energy devices: bake the compound in a microwave oven. “This is a major advance in the graphene field,” said Manish Chhowalla, professor and associate chair in the Department of Materials Science and Engineering in Rutgers’ School of Engineering. “This simple microwave treatment leads to exceptionally high-quality graphene with properties approaching those in pristine graphene.”The discovery was made by post-doctoral associates and undergraduate students in the department, said Chhowalla, who is also the director of the Rutgers Institute for Advanced Materials, Devices and Nanotechnology. The easiest way to make large quantities of graphene is to exfoliate graphite into individual graphene sheets by using chemicals. The downside of this approach is that side reactions occur with oxygen – forming graphene oxide that is electrically non-conducting, which makes it less useful for products.Removing oxygen from graphene oxide to obtain high-quality graphene has been a major challenge over the past two decades for the scientific community working on graphene. Oxygen distorts the pristine atomic structure of graphene and degrades its properties. Chhowalla and his group members found that baking the exfoliated graphene oxide for just one second in a 1,000-watt microwave oven, like those used in households across America, can eliminate virtually all of the oxygen from graphene oxide.

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A team of researchers, led by Boston University College of Engineering (ENG) PhD candidate Farrukh Mateen (ENG’18) and Raj Mohanty, a professor of physics at BU’s College of Arts & Sciences (CAS), are closing in on a solution. They have built a tiny micromechanical device and turned it on and off with one nanowatt of power—that’s a billionth of a watt—from three feet away. The device is a miniature sandwich of gold and aluminum nitride that vibrates, or resonates, at microwave frequencies. The tiny resonator is only 100 micrometers across—a little wider than the width of a human hair. “Wireless power is not new,” says Mateen. “Nikola Tesla demonstrated it at the 1893 World’s Fair; but we believe this is the first time it’s been used with a micromechanical resonator.” In a second round of experiments, the device achieved an impressive 15 percent efficiency using a higher radio frequency. The most promising application for this type of device lies in the emerging field of optogenetics: shining light on genetically modified brain cells to make them behave in a certain way. The field offers great potential for neuroscience research, as well as possible treatments for neurological disorders like Parkinson’s disease. But to plant a device in the body, especially the brain, is challenging. It needs to be tiny and efficient, low-power and low-radiation. Power must travel to the device quickly, through bone and brain tissue. “You don’t want to have to change batteries every day,” says Mohanty, corresponding author on both papers, “and you don’t want to fry your brain.”

Graphene oxide has been hailed as a veritable wonder material; when incorporated into nanocellulose foam, the lab-created substance is light, strong and flexible, conducting heat and electricity quickly and efficiently. Now, a team of engineers at Washington University in St. Louis has found a way to use graphene oxide sheets to transform dirty water into drinking water, and it could be a global game-changer. “We hope that for countries where there is ample sunlight, such as India, you’ll be able to take some dirty water, evaporate it using our material, and collect fresh water,” said Srikanth Singamaneni, associate professor of mechanical engineering and materials science at the School of Engineering & Applied Science. The new approach combines bacteria-produced cellulose and graphene oxide to form a bi-layered biofoam. “The process is extremely simple,” Singamaneni said. “The beauty is that the nanoscale cellulose fiber network produced by bacteria has excellent ability move the water from the bulk to the evaporative surface while minimizing the heat coming down, and the entire thing is produced in one shot.” “The design of the material is novel here,” Singamaneni said. “You have a bi-layered structure with light-absorbing graphene oxide filled nanocellulose at the top and pristine nanocellulose at the bottom. When you suspend this entire thing on water, the water is actually able to reach the top surface where evaporation happens. “Light radiates on top of it, and it converts into heat because of the graphene oxide — but the heat dissipation to the bulk water underneath is minimized by the pristine nanocellulose layer. You don’t want to waste the heat; you want to confine the heat to the top layer where the evaporation is actually happening.” The cellulose at the bottom of the bi-layered biofoam acts as a sponge, drawing water up to the graphene oxide where rapid evaporation occurs. The resulting fresh water can easily be collected from the top of the sheet.

Biologists are increasingly interested in the behaviour of individual cells, rather than the one of an entire cell population. A new method developed at Eidgenössische Technische Hochschule (ETH) Zürich could revolutionise single cell analysis. The technology uses the world’s smallest syringe to sample the content of individual cells for molecular analyses. ETH researchers have developed a method using a nanosyringe whose tiny needle is able to penetrate single living cells and extract their content. The technology can be used for cell cultures, for example, in order to investigate the interior of the cells. This allows scientists to identify the differences between individual cells at the molecular level, as well as to identify and analyse rare cell types. “Our method opens up new frontiers in biological research. It is the start of a whole new chapter, so to speak”, says Professor Julia Vorholt from the Department of Biology. The new method has numerous advantages: researchers can sample individual cells of a tissue culture directly in the petri dish. “This means we can study how a cell affects its neighbouring cells”, says Orane Guillaume-Gentil, a postdoc in Professor Vorholt’s research group. This type of investigation is not possible using conventional methods, as molecular analyses generally require the cells to first be physically separated and then destroyed. On top of that, the microscopic needle can be controlled so precisely that scientists are able either to harvest the content of the nucleus or collect the intracellular fluid surrounding the nucleus, the cytosol. Last but not least, the researchers can determine the amount of intracellular material they extract with incredible accuracy, down to one tenth of a pictolitre (one trillionth of a litre). By way of comparison: the volume of a cell is 10 to 100 times bigger.

The fountain of youth may reside in an embryonic stem cell gene named Nanog. In a series of experiments at the University at Buffalo, the gene kicked into action dormant cellular processes that are key to preventing weak bones, clogged arteries and other telltale signs of growing old. The findings also show promise in counteracting premature aging disorders such as Hutchinson-Gilford progeria syndrome. “Our research into Nanog is helping us to better understand the process of aging and ultimately how to reverse it,” says Stelios T. Andreadis, PhD, professor and chair of the Department of Chemical and Biological Engineering at the UB School of Engineering and Applied Sciences, and the study’s lead author. To battle aging, the human body holds a reservoir of nonspecialized cells that can regenerate organs. These cells are called adult stem cells, and they are located in every tissue of the body and respond rapidly when there is a need. But as people age, fewer adult stem cells perform their job well, a scenario which leads to age-related disorders. Reversing the effects of aging on adult stem cells, essentially rebooting them, can help overcome this problem. In the study, Panagiotis Mistriotis, a graduate student in Andreadis’ lab and first author of the study, introduced Nanog into aged stem cells. He found that Nanog opens two key cellular pathways: Rho-associated protein kinase (ROCK) and Transforming growth factor beta (TGF-β). In turn, this jumpstarts dormant proteins (actin) into building cytoskeletons that adult stem cells need to form muscle cells that contract. Force generated by these cells ultimately helps restore the regenerative properties that adult stem cells lose due to aging.